Method for pressure relief in gas containers and means for carrying out the method



1965 B. WlDELL 3,166,479

METHOD FOR PRESSURE RELIEF IN GAS CONTAINERS AND MEANS FOR CARRYING OUTTHE METHOD Filed May 21. 1962 I INVENTOR. 3 y WHIP/l United StatesPatent 3,166,479 NEETHOD FOR PRESSURE RELIEF IN GAS CQN- TAINERS ANDMEANS FOR CARRYING OUT THE METHOD Biol-11 Widell, Vasteras, Sweden,assignor to Allmtinna Svenska Elektriska Aktieholaget, Vasteras, Sweden,:1 Swedish corporation Filed May 21, 1%2, Ser. No. 196,105 Claimspriority, application Sweden, May 26, 1961, 5,496/ 61 1 Claim. (Cl.176-37) The present invention relates to a method of relieving thepressure in gas containers and a means for carrying out the method.

The problem which arises when relieving the pressure in gas containerswill be dealt with more in detail for a case chosen as an example,namely when the gas container is a component in a gas circulationcircuit in a homogeneous boiling reactor, whereby it contains stronglyradioactive fission gases. If a fault should occur in the reactoroperation, the pressure in the gas container could exceed that permittedand it has therefore been proposed to place the gas container incommunication with a gas tank serving as collecting vessel for the gasand having a displaceable lid, in order when necessary to be able torelieve the pressure in the gas container. The method of using such agas tank for pressure relief is, however, impaired by serious drawbackssince it is exteremely difiicult to eiiect a reliable sealing betweenthe displaceable lid and the gas tank itself, so that the risk ofleakage from the gas container of strongly radioactive substances ispresent.

Another way of arranging pressure relief in the gas container is toplace it in communication with one or several very large closedcollecting vessels freely communicating with each other and having nomovable parts. The use of such large vessels, however, also involvesdisadvantages, partly because it is unfavourable to use large vesselssince they require a considerable amount of space and partly because itis difiicult to manufacture very large vessels and leak-test them.

By means of the present invention the mentioned drawbacks are avoided inthe described collecting vessels and it is possible to use completelyclosed collecting vessels without movable parts and sealing means andwhich require considerably less space than the above mentioned largeclosed collecting vessels.

The invention relates to a method of relieving the pressure in gascontainers containing a gas under pressure, forv example a gas containercontaining collected radioactive fission gas formed during operation ina homogeneous reactor, whereby the main part of the gas is transferredto collecting vessels for the gas, connected to the gas container. Theinvention is characterized in that the gas container with openable andclosable connection conduits is connected to several collecting vessels,and that the gas container is placed in open communication with onecollecting vessel at a time and the open communication between the gascontainer and one collecting vessel is closed after the pressure in thegas container and the collecting vessel has become substan tially equal,before the gas container is placed in open communication with anothercollecting vessel. If the collecting vessel with which the gas containeris last placed in open communication is evacuated to a pressure belowatmospheric pressure before the open communication is established, theparticular advantage is attained that the pressure in the gas containermay be reduced to below atmospheric pressure so that leakage isprevented from this to the surroundings through a possibly arisingcrack, which might be the cause of the presuranium 235.

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sure relief being made. To carry out the method it is suitable to use ameans in which the collecting vessels are arranged along a main conduitconnected to the gas container and the collecting vessels are connectedto the main conduit by means of connection conduits containing openableand closable valves, but the collecting vessels could also, viaconnection conduits having such valves, be directly connected to the gascontainer Without an intermediate main conduit. It is particularlyadvantageous if the valves in the different connection conduits consistof automatically controlled valves having successively falling openingpressure and successively falling closing pressure.

The invention will be further explained by describing one embodimentwith refernece to the accompanying figure which shows a schematicalpicture of a homogeneous boiling reactor with pertaining gas circulationcircult.

The boiling reactor core 2 of the reactor vessel 1, which core containslight or heavy water as moderator, in the device according to thefigure, gives off aqueous steam which via the conduit 3 rises into thecondenser 4. Apart from the mentioned moderator, the reactor core 2 mayfor example consist of thorium oxide dispersed in the moderator, andenriched material uranium 233 or The steam is condensed in the condenserand gives off its heat content to the feeding water supplied at 5 andled off at 6. The condensate is returned to the reactor core via theconduit 7. The homogeneous boiling reactor also gives off oxyhydrogengas because of the radiolytic splitting of the moderator. Theoxyhydrogen gas is recombined in the recombiner 8. The conduit betweenthe condenser 4 and the recombiner has been designated 9. Possiblyremaining steam from the condenser 4, together with aqueous steam formedin the recombiner and possibly remaining oxyhydrogen, is led via theconduit 11) to a tail condenser 11 which is suitably supplied withfeeding water on the secondary side at 12. This water may also beutilized for cooling the condenser 4, whereby it enters the secondaryside of the condenser 4 via the conduit 5 as feeding water. Condensateformed in the tail condenser is returned to the reactor core via theconduit 13. The shown system for external recombination of theoxyhydrogen gas, consisting essentially of the recombiner 8 and the tailcondenser 11, is unnecessary if interal recombination can be effected,for example by the addition of catalysts to the reactor fuel.

The steam rising from the reactor core is supplied via the conduit 14with permanent gas, for example hydrogen, deuterium, oxygen, helium,whereby the choice of gas is influenced by the chemical composition ofthe reactor core. The permanent gas, which comes from the gas container15, is thus mixed with the steam and is returned to the container 15when it has passed the condenser 4 and the possibly connectedarrangements 8 and 11, via the conduit 16. The circulation of thepermanent gas in this closed system is carried out by the gas pump 17.The reason for the introduction of permanent gas into the system is toavoid the fission gas reaching a noxious concentration in the reactorcore. Due to the presence of the permanent gas, fission gases formeddistribute themselves in a favourable way between the liquid phase inthe reactor core and the gas phase. Large amounts of radioactive gasunder pressure are collected in the container 15 during the reactoroperation. In accordance with the invention the gas container 15 is viaa main conduit 18 placed in communication with a number, in the showncase seven, of collecting vessels, in the Figure designated 19a-g. Thevessels 1911- may suitably have atmospheric pressure while the vessel19g may suitably be evacuated to a pressure below atmospheric pressure.In each conduit Ztlzr-g between the main conduit 18 and 3 respectivecollecting vessels Hit-g, an opening valve 21ag is arranged, and inseries with this a closing valve 22ag. If the pressure in the container15 exceeds that permitted, for example due to incomplete condensation inthe condenser 4, or if a leakage occurs in the gas system, the container15 is relieved of pressure by the utilization of the collecting vessels19ag. Thereby the valve Zia is first opened, which as the rest of theopening valves Zibg is closed from the beginning. This causes a pressureequalization to take place between the container 15 and the collectingvessel 1%. When the pressure in the vessel 1% approaches or has becomethe same as that in the container 15, the closing valve 22a is closed,which as the other closing valves 22b-g, is open from the beginning,after which the opening valve 21b is opened. Thus part of the gas in thecontainer 15 is transferred to the vessel 1%. When the pressure in thevessel 1% approaches the reduced pressure in the container 15, theclosing valve 22b is closed, and the opening valve 210 is then opened.The same procedure is repeated for the vessel 19c and the other vessels1951-5 until the main part of the gas quantity in the container 15 hasbeen distributed in the collecting vessels 19a-g. If at the outset thevessel 15 g has lower pressure than atmospheric pressure, the finalpressure in the gas container 15 may be reduced below atmosphericpressure, which is an advantage if the reason for the pressure relief isa leakage arising in the container 15 or in the gas circulation circuitof the reactor. The opening and closing of each valve may with advantagetake place automatically and is then suitably controlled in a known waybe means of pressure sensing means in the gas container and respectivecollecting vessels. Each mm. Hg, by using the general equation for idealgases,

connection conduit 2-lDa-g need not in accordance with g the figurecontain two valves, one'opening and one closing valve, but these couldbe replaced by a single valve which is then used both when opening andwhen closing a the respective connection conduits.

The actual operation conditions and dimensioning of the means shown inthe figure will be given in the following. At the start of the pressurerelief in the container 15 the pressure and temperature in the reactorpart are presumed to be 70 atmospheres and 286 C. The total quantity ofgas in the system is presumed to be 36 mfi, 6 111. being in thecontainer 15. The collecting vessels fizz-g are double sheathed and areprovided with cooling means between the sheaths. All collecting vesselsare cylindrical and 6 m. high. The diameter of the vessel 19a is 1.6 m.,of the vessel 19b 2 m., of the vessels 19c and 19d 2.5 111., and of thevessels we, 19 and 19 g 3 m. If it is assumed that the temperature doesnot alter during the pressure relief and that the pressure in thepressure in the different collecting vessels after completed pressurerelief may easily be calculated to 53 atmospheres for the vessel 19a,34.5 atmospheres for the vessel 1%, l9 atmospheres for the vessel 19c,10.5 atmospheres for the vessel 1%, 4.8 atmospherestor the vessel 192,2.2 atmospheres for the vessel 1% and 1 atmosphere for the vessel Hg.The total volume in the vessels ag, which relieve the gas'container 15so that the pressure in it becomes 1 atmosphere, is 217 111. In order toobtain the same pressure relic; in the container 15 with a singleevacuated collecting vessel or several evacuated collecting vesselscommunicating with each other, a volume of 2520 111. would be required.

Although the invention is described particularly'for the case where-thepressure relief is carried out from a container containing radioactivegases from a homogeneous reactor, it is'obvious that it may also be used011 other occasions when it is necessary to relieve the pressure in agas container. 7

I claim:

Method of relieving'prcssure in a gas container containing a mass of gasunder pressure which comprises connecting the gas container successivelyto each of a plurality of gas collecting vessels while maintaining itout of communication with any other of the vessels, and maintaining theconnection each time until the pressure in the collecting vessel withwhich the container is connected reaches substantial equilibrium withthe pressure of the gas in the container, said gas container beingconnected to a homogeneous nuclear reactor and containing collectedradioactive fission gas formed during operation of the homogeneousreactor, and the last collecting vessel with which the gas container isconnected being evacuated to sub-atmospheric pressure before theconnection is made.

References Cited by the Examiner UNITED STATES PATENTS 3,036,779 5/62Hansen 137 593 X 3,068,164 12/62 Colesetal 23-289 3,089,513 5/63 Kirk"137-593 FOREIGN PATENTS 631,068 10/49 GreatBritain.

631,069 10/49 Great Britain.

CARL D. QUARFORTH. Primal-v Examiner.

